This invention is in the area of pharmaceutical chemistry, and in particular, includes 2xe2x80x2-fluoronucleosides and methods for their preparation and use.
Synthetic nucleosides such as 5-iodo-2xe2x80x2-deoxyuridine and 5-fluoro-2xe2x80x2-deoxyuridine have been used for the treatment of cancer and herpes viruses for a number of years. Since the 1980""s, synthetic nucleosides have also been a focus of interest for the treatment of HIV, hepatitis, and Epstein-Barr viruses.
In 1981, acquired immune deficiency syndrome (AIDS) was identified as a disease that severely compromises the human immune system, and that almost without exception leads to death. In 1983, the etiological cause of AIDS was determined to be the human immunodeficiency virus (HIV). In 1985, it was reported that the synthetic nucleoside 3xe2x80x2-azido-3xe2x80x2-deoxythymidine (AZT) inhibits the replication of human immunodeficiency virus. Since then, a number of other synthetic nucleosides, including 2xe2x80x2,3xe2x80x2-dideoxyinosine (DDI), 2xe2x80x2, 3xe2x80x2-dideoxycytidine (DDC), and 2xe2x80x2,3xe2x80x2-dideoxy-2xe2x80x2,3xe2x80x2-didehydrothymidine (D4T), have been proven to be effective against HIV. After cellular phosphorylation to the 5xe2x80x2-triphosphate by cellular kinases, these synthetic nucleosides are incorporated into a growing strand of viral DNA, causing chain termination due to the absence of the 3xe2x80x2-hydroxyl group. They can also inhibit the viral enzyme reverse transcriptase.
The success of various synthetic nucleosides in inhibiting the replication of HIV in vivo or in vitro has led a number of researchers to design and test nucleosides that substitute a heteroatom for the carbon atom at the 3xe2x80x2-position of the nucleoside. European Patent Application Publication No. 0 337 713 and U.S. Pat. No. 5,041,449, assigned to BioChem Pharma, Inc., disclose racemic 2-substituted-4-substituted-1,3-dioxolanes that exhibit antiviral activity. U.S. Pat. No. 5,047,407 and European Patent Application No. 0 382 526, also assigned to BioChem Pharma, Inc., disclose that a number of racemic 2-substituted-5-substituted-1,3-oxathiolane nucleosides have antiviral activity, and specifically report that the racemic mixture of 2-hydroxymethyl-5-(cytosin-1-yl)-1,3-oxathiolane (referred to below as BCH-189) has approximately the same activity against HIV as AZT, with little toxicity. The (xe2x88x92)-enantiomer of the racemate BCH-189, known as 3TC, which is covered by U.S. Pat. No. 5,539,116 to Liotta et al., is currently sold for the treatment of HIV in combination with AZT in humans in the U.S.
It has also been disclosed that cis-2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane (xe2x80x9cFTCxe2x80x9d) has potent HIV activity. Schinazi, et al., xe2x80x9cSelective Inhibition of Human Immunodeficiency viruses by Racemates and Enantiomers of cis-5-Fluoro-1-[2-(Hydroxymethyl)-1,3-Oxathiolane-5-yl]Cytosinexe2x80x9d Antimicrobial Agents and Chemotherapy, November 1992, pp. 2423-2431. See also U.S. Pat. No. 5,210,085; WO 91/11186, and WO 92/14743.
Another virus that causes a serious human health problem is the hepatitis B virus (referred to below as xe2x80x9cHBVxe2x80x9d). HBV is second only to tobacco as a cause of human cancer. The mechanism by which HBV induces cancer is unknown. It is postulated that it may directly trigger tumor development, or indirectly trigger tumor development through chronic inflammation, cirrhosis, and cell regeneration associated with the infection.
After a two to six month incubation period in which the host is unaware of the infection, HBV infection can lead to acute hepatitis and liver damage, that causes abdominal pain, jaundice, and elevated blood levels of certain enzymes. HBV can cause fulminant hepatitis, a rapidly progressive, often fatal form of the disease in which massive sections of the liver are destroyed.
Patients typically recover from acute hepatitis. In some patients, however, high levels of viral antigen persist in the blood for an extended, or indefinite, period, causing a chronic infection. Chronic infections can lead to chronic persistent hepatitis. Patients infected with chronic persistent HBV are most common in developing countries. By mid-1991, there were approximately 225 million chronic carriers of HBV in Asia alone, and worldwide, almost 300 million carriers. Chronic persistent hepatitis can cause fatigue, cirrhosis of the liver, and hepatocellular carcinoma, a primary liver cancer.
In western industrialized countries, high risk groups for HBV infection include those in contact with HBV carriers or their blood samples. The epidemiology of HBV is very similar to that of acquired immune deficiency syndrome, which accounts for why HBV infection is common among patients infected with HIV or AIDS. However, HBV is more contagious than HIV.
Both FTC and 3TC exhibit activity against HBV. Furman, et al., xe2x80x9cThe Anti-Hepatitis B Virus Activities, Cytotoxicities, and Anabolic Profiles of the (xe2x88x92) and (+) Enantiomers of cis-5-Fluoro-1-[2-(Hydroxymethyl)-1,3-oxathiolane-5-yl]-Cytosinexe2x80x9d Antimicrobial Agents and Chemotherapy, December 1992, pp. 2686-2692; and Cheng, et al., Journal of Biological Chemistry, Volume 267(20), pp. 13938-13942 (1992).
A human serum-derived vaccine has been developed to immunize patients against HBV. While it has been found effective, production of the vaccine is troublesome because the supply of human serum from chronic carriers is limited, and the purification procedure is long and expensive. Further, each batch of vaccine prepared from different serum must be tested in chimpanzees to ensure safety. Vaccines have also been produced through genetic engineering. Daily treatments with a-interferon, a genetically engineered protein, has also shown promise.
Hepatitis C virus (xe2x80x9cHCVxe2x80x9d) is the major causative agent for post-transfusion and for sporadic non A, non B hepatitis (Alter, H. J. (1990) J. Gastro. Hepatol. 1:78-94; Dienstag, J. L. (1983) Gastro 85:439-462). Despite improved screening, HCV still accounts for at least 25% of the acute viral hepatitis in many countries (Alter, H. J. (1990) supra; Dienstag, J. L. (1983) supra; Alter M. J. et al. (1990a) J.A.M.A. 264:2231-2235; Alter M. J. et al (1992) N. Engl. J. Med. 327:1899-1905; Alter, M. J. et al. (1990b) N. Engl. J. Med. 321:1494-1500). Infection by HCV is insidious in a high proportion of chronically infected (and infectious) carriers who may not experience clinical symptoms for many years. The high rate of progression of acute infection to chronic infection (70-100%) and liver disease ( greater than 50%), its world-wide distribution and lack of a vaccine make HCV a significant cause of morbidity and mortality.
A tumor is an unregulated, disorganized proliferation of cell growth. A tumor is malignant, or cancerous, if it has the properties of invasiveness and metastasis. Invasiveness refers to the tendency of a tumor to enter surrounding tissue, breaking through the basal laminas that define the boundaries of the tissues, thereby often entering the body""s circulatory system. Metastasis refers to the tendency of a tumor to migrate to other areas of the body and establish areas of proliferation away from the site of initial appearance.
Cancer is now the second leading cause of death in the United States. Over 8,000,000 persons in the United States have been diagnosed with cancer, with 1,208,000 new diagnoses expected in 1994. Over 500,000 people die annually from the disease in this country.
Cancer is not fully understood on the molecular level. It is known that exposure of a cell to a carcinogen such as certain viruses, certain chemicals, or radiation, leads to DNA alteration that inactivates a xe2x80x9csuppressivexe2x80x9d gene or activates an xe2x80x9concogenexe2x80x9d. Suppressive genes are growth regulatory genes, which upon mutation, can no longer control cell growth. Oncogenes are initially normal genes (called prooncongenes) that by mutation or altered context of expression become transforming genes. The products of transforming genes cause inappropriate cell growth. More than twenty different normal cellular genes can become oncogenes by genetic alteration. Transformed cells differ from normal cells in many ways, including cell morphology, cell-to-cell interactions, membrane content, cytoskeletal structure, protein secretion, gene expression and mortality (transformed cells can grow indefinitely).
All of the various cell types of the body can be transformed into benign or malignant tumor cells. The most frequent tumor site is lung, followed by colorectal, breast, prostate, bladder, pancreas, and then ovary. Other prevalent types of cancer include leukemia, central nervous system cancers, including brain cancer, melanoma, lymphoma, erythroleukemia, uterine cancer, and head and neck cancer.
Cancer is now primarily treated with one or a combination of three years of therapies: surgery, radiation, and chemotherapy. Surgery involves the bulk removal of diseased tissue. While surgery is sometimes effective in removing tumors located at certain sites, for example, in the breast, colon, and skin, it cannot be used in the treatment of tumors located in other areas, such as the backbone, nor in the treatment of disseminated neoplastic conditions such as leukemia.
Chemotherapy involves the disruption of cell replication or cell metabolism. It is used most often in the treatment of leukemia, as well as breast, lung, and testicular cancer.
There are five major classes of chemotherapeutic agents currently in use for the treatment of cancer: natural products and their derivatives; anthacyclines; alkylating agents; antiproliferatives (also called antimetabolites); and hormonal agents. Chemotherapeutic agents are often referred to as antineoplastic agents.
The alkylating agents are believed to act by alkylating and cross-linking guanine and possibly other bases in DNA, arresting cell division. Typical alkylating agents include nitrogen mustards, ethyleneimine compounds, alkyl sulfates, cisplatin, and various nitrosoureas. A disadvantage with these compounds is that they not only attach malignant cells, but also other cells which are naturally dividing, such as those of bone marrow, skin, gastro-intestinal mucosa, and fetal tissue.
Antimetabolites are typically reversible or irreversible enzyme inhibitors, or compounds that otherwise interfere with the replication, translation or transcription of nucleic acids.
Several synthetic nucleosides have been identified that exhibit anticancer activity. A well known nucleoside derivative with strong anticancer activity is 5-fluorouracil. 5-Fluorouracil has been used clinically in the treatment of malignant tumors, including, for example, carcinomas, sarcomas, skin cancer, cancer of the digestive organs, and breast cancer. 5-Fluorouracil, however, causes serious adverse reactions such as nausea, alopecia, diarrhea, stomatitis, leukocytic thrombocytopenia, anorexia, pigmentation, and edema. Derivatives of 5-fluorouracil with anti-cancer activity have been described in U.S. Pat. No. 4,336,381, and in Japanese patent publication Nos. 50-50383, 50-50384, 50-64281, 51-146482, and 53-84981.
U.S. Pat. No. 4,000,137 discloses that the peroxidate oxidation product of inosine, adenosine, or cytidine with methanol or ethanol has activity against lymphocytic leukemia.
Cytosine arabinoside (also referred to as Cytarabin, araC, and Cytosar) is a nucleoside analog of deoxycytidine that was first synthesized in 1950 and introduced into clinical medicine in 1963. It is currently an important drug in the treatment of acute myeloid leukemia. It is also active against acute lymphocytic leukemia, and to a lesser extent, is useful in chronic myelocytic leukemia and non-Hodgkin""s lymphoma. The primary action of araC is inhibition of nuclear DNA synthesis. Handschumacher, R. and Cheng, Y., xe2x80x9cPurine and Pyrimidine Antimetabolitesxe2x80x9d, Cancer Medicine, Chapter XV-1, 3rd Edition, Edited by J. Holland, et al., Lea and Febigol, publishers.
5-Azacytidine is a cytidine analog that is primarily used in the treatment of acute myelocytic leukemia and myelodysplastic syndrome.
2-Fluoroadenosine-5xe2x80x2-phosphate (Fludara, also referred to as FaraA)) is one of the most active agents in the treatment of chronic lymphocytic leukemia. The compound acts by inhibiting DNA synthesis. Treatment of cells with F-araA is associated with the accumulation of cells at the G1/S phase boundary and in S phase; thus, it is a cell cycle S phase-specific drug. Incorporation of the active metabolite, F-araATP, retards DNA chain elongation. F-araA is also a potent inhibitor of ribonucleotide reductase, the key enzyme responsible for the formation of DATP.
2-Chlorodeoxyadenosine is useful in the treatment of low grade B-cell neoplasms such as chronic lymphocytic leukemia, non-Hodgkinsxe2x80x2 lymphoma, and hairy-cell leukemia.
In designing new biologically active nucleosides, there have been a number of attempts to incorporate a fluoro substituent into the carbohydrate ring of the nucleoside. Fluorine has been suggested as a substituent because it might serve as an isopolar and isosteric mimic of a hydroxyl group as the Cxe2x80x94F bond length (1.35 xc3x85) is so similar to the Cxe2x80x94O bond length (1.43 xc3x85) and because fluorine is a hydrogen bond acceptor. Fluorine is capable of producing significant electronic changes in a molecule with minimal steric perturbation. The substitution of fluorine for another group in a molecule can cause changes in substrate metabolism because of the high strength of the Cxe2x80x94F bond (116 kcal/mol vs. Cxe2x80x94H=100 kcal/mol).
A number of references have reported the synthesis and use of 2xe2x80x2-arabinofluoro-nucleosides (i.e., nucleosides in which a 2xe2x80x2-fluoro group is in the xe2x80x9cupxe2x80x9d-configuration). There have been several reports of 2-fluoro-xcex2-D-arabinofuranosyl nucleosides that exhibit activity against hepatitis B and herpes. See, for example, U.S. Pat. No. 4,666,892 to Fox, et al.; U.S. Pat. No. 4,211,773 to Lopez, et al; Su, et al., Nucleosides. 136, xe2x80x9cSynthesis and Antiviral Effects of Several 1-(2-Deoxy-2-fluoro-xcex2-D-arabinofuranosyl)-5-alkyluracils.xe2x80x9d xe2x80x9cSome Structure-Activity Relationships,xe2x80x9d J. Med. Chem., 1986, 29, 151-154; Borthwick, et al., xe2x80x9cSynthesis and Enzymatic Resolution of Carbocyclic 2xe2x80x2-Ara-fluoro-Guanosine: A Potent New Anti-Herpetic Agent,xe2x80x9d J. Chem. Soc., Chem. Commun, 1988; Wantanabe, et al., xe2x80x9cSynthesis and Anti-HIV Activity of 2xe2x80x2-xe2x80x9cUpxe2x80x9d-Fluoro Analogues of Active Anti-Aids Nucleosides 3xe2x80x2-Azido-3xe2x80x2-deoxythymidine (AZT) and 2xe2x80x2,3xe2x80x2-dideoxycytidine (DDC),xe2x80x9d J. Med. Chem. 1990, 33, 2145-2150; Martin, et al., xe2x80x9cSynthesis and Antiviral Activity of Monofluoro and Difluoro Analogues of Pyrimidine Deoxyribonucleosides against Human Immunodeficiency Virus (HIV-1),xe2x80x9d J. Med., Chem. 1990, 33, 2137-2145; Sterzycki, et al., xe2x80x9cSynthesis and Anti-HIV Activity of Several 2xe2x80x2-Fluoro-Containing Pyrimidine Nucleosides,xe2x80x9d J. Med Chem. 1990, as well as EPA 0 316 017 also filed by Sterzycki, et al.; and Montgomery, et al., xe2x80x9c9-(2-Deoxy-2-fluoro-xcex2-D-arabinofuranosyl)guanine: A Metabolically Stable Cytotoxic Analogue of 2xe2x80x2-Deoxyguanosine.xe2x80x9d U.S. Pat. No. 5,246,924 discloses a method for treating a hepatitis infection that includes the administration of 1-(2xe2x80x2-deoxy-2xe2x80x2-fluoro-xcex2-D-arabinofuranosyl)-3-ethyluracil), also referred to as xe2x80x9cFEAU.xe2x80x9d U.S. Pat. No. 5,034,518 discloses 2-fluoro-9-(2-deoxy-2-fluoro-xcex2-D-arabinofuranosyl)adenine nucleosides which exhibit anticancer activity by altering the metabolism of adenine nucleosides by reducing the ability of the compound to serve as a substrate for adenosine. EPA 0 292 023 discloses that certain xcex2-D-2xe2x80x2-fluoroarabinonucleosides are active against viral infections.
U.S. Pat. No. 5,128,458 discloses xcex2-D-2xe2x80x2,3xe2x80x2-dideoxy-4xe2x80x2-thioribonucleosides as antiviral agents. U.S. Pat. No. 5,446,029 discloses that 2xe2x80x2,3xe2x80x2-dideoxy-3xe2x80x2-fluoronucleosides have antihepatitis activity.
European Patent Application No. 0 409 227 A2 discloses certain 3xe2x80x2-substituted xcex2-D-pyrimidine and purine nucleosides for the treatment of hepatitis B.
It has also been disclosed that L-FMAU (2xe2x80x2-fluoro-5-methyl-xcex2-L-arabinofuranosyluracil) is a potent anti-HBV and anti-EBV agent. See Chu, et al., xe2x80x9cUse of 2xe2x80x2-Fluoro-5-methyl-xcex2-L-arabinofuranosyluracil as a Novel Antiviral Agent for Hepatitis B Virus and Epstein-Barr Virusxe2x80x9d Antimicrobial Agents and Chemotherapy, April 1995 pages. 979-98 1; Balakrishna, et al., xe2x80x9cInhibition of Hepatitis B Virus by a Novel L-Nucleoside, 2xe2x80x2-Fluoro-5-Methyl-xcex2-L-arabinofuranosyl Uracil,xe2x80x9d Antimicrobial Agents and Chemotherapy, Feburary 1996, pages 380-356; U.S. Pat. Nos. 5,587,362; 5,567,688; and 5,565,438.
U.S. Pat. Nos. 5,426,183 and 5,424,416 disclose processes for preparing 2xe2x80x2-deoxy-2xe2x80x2, 2xe2x80x2-difluoronucleosides and 2xe2x80x2-deoxy-2xe2x80x2-fluoro nucleosides. See also xe2x80x9cKinetic Studies of 2xe2x80x2, 2xe2x80x2-difluorodeoxycytidine (Gemcitabine) with Purified Human Deoxycytidine Kinase and Cytidine Deaminase,xe2x80x9d BioChemical Pharmacology, Vol. 45 (No. 9) pages 4857-1861, 1993.
U.S. Pat. No. 5,446,029 to Eriksson, et al., discloses that certain 2xe2x80x2,3xe2x80x2-dideoxy-3xe2x80x2-fluoronucleosides have hepatitis B activity. U.S. Pat. No. 5,128,458 discloses certain 2xe2x80x2, 3xe2x80x2-dideoxy-4xe2x80x2-thioribonucleosides wherein the 3xe2x80x2-substituent is H, azide or fluoro. WO 94/14831 discloses certain 3xe2x80x2-fluoro-dihydropyrimidine nucleosides. WO 92/08727 discloses xcex2-L-2xe2x80x2-deoxy-3xe2x80x2-fluoro-5-substituted uridine nucleosides for the treatment of herpes simplex 1 and 2.
EPA Publication No. 0 352 248 discloses a broad genus of L-ribofuranosyl purine nucleosides for the treatment of HIV, herpes, and hepatitis. While certain 2xe2x80x2-fluorinated purine nucleosides fall within the broad genus, there is no information given in the specification on how to make these compounds in the specification, and they are not among specifically disclosed or the preferred list of nucleosides in the specification. The specification does disclose how to make 3xe2x80x2-ribofuranosyl fluorinated nucleosides. A similar specification is found in WO 88/09001, filed by Aktiebolaget Astra.
European Patent Application 0 357 571 discloses a broad group of xcex2-D and xcex1-D pyrimidine nucleosides for the treatment of AIDS which among the broad class generically includes nucleosides that can be substituted in the 2xe2x80x2 or 3xe2x80x2-position with a fluorine group. Among this broad class, however, there is no specific disclosure of 2xe2x80x2-fluorinated nucleosides or a method for their production.
EPA 0 463 470 discloses a process for the preparation of (5S)-3-fluoro-tetrahydro-5-[(hydroxy)methyl]-2-(3H)-furanone, a known intermediate in the manufacture of 2xe2x80x2-fluoro-2xe2x80x2, 3xe2x80x2-dideoxynucleosides such as 2xe2x80x2-fluoro-2xe2x80x2,3xe2x80x2-dideoxycytidine.
U.S. Ser. No. 07/556,713 discloses xcex2-D-2xe2x80x2-fluoroarabinofuranosyl nucleosides, and a method for their production, which are intermediates in the synthesis of 2xe2x80x2,3xe2x80x2-dideoxy-2xe2x80x2-fluoroarabinosyl nucleosides.
U.S. Pat. No. 4,625,020 discloses a method of producing 1-halo-2-deoxy-2-fluoroarabinofuranosyl derivatives bearing protective ester groups from 1,3,5-tri-O-acyl-ribofuranose.
There appears to be a lack of disclosure of xcex2-L-2xe2x80x2-fluoro-riboftiranosyl nucleosides for medicinal uses, including for HIV, hepatitis (B or C), or proliferative conditions. At least with respect to 2xe2x80x2-ribofuranosyl nucleosides, this may be because of the prior perceived difficulty in placing a fluoro group in the 2xe2x80x2-ribofiuranosyl configuration. With respect to L-2xe2x80x2-fluoro-2xe2x80x2, 3xe2x80x2-unsaturated purine nucleosides, it may be because the purine nucleosides are unstable in acidic media, resulting in glycosyl bond cleavage.
In light of the fact that HIV acquired immune deficiency syndrome, AIDS-related complex, and hepatitis B and C viruses have reached epidemic levels worldwide, and have tragic effects on the infected patient, there remains a strong need to provide new effective pharmaceutical agents to treat these diseases that have low toxicity to the host. Further, there is a need to provide new antiproliferative agents.
Therefore, it is an object of the present invention to provide a method and composition for the treatment of human patients infected with hepatitis B or C.
It is another object of the present invention to provide a method and composition for the treatment of human patients infected with HIV.
It is a further object of the present invention to provide new antiproliferative agents.
It is still another object of the present invention to provide a new process for the preparation of 2xe2x80x2-fluoro-ribofuranosyl nucleosides.
It is yet another object of the present invention to provide a new process for the preparation of 2xe2x80x2,3xe2x80x2-dideoxy-2xe2x80x2,3xe2x80x2-didehydro-2xe2x80x2-fluoro-L-glycero-pent-2-eno-furanosyl nucleosides.
In one embodiment of the invention, a 2xe2x80x2-xcex1-fluoro-nucleoside is provided of the structure: 
wherein
Base is a purine or pyrimidine base as defined further herein;
R1 is OH, H, OR3, N3, CN, halogen, including F, or CF3, lower alkyl, amino, loweralkylarnino, di(lower)alkylamino, or alkoxy, and base refers to a purine or pyrimidine base;
R2 is H, phosphate, including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug; acyl, or other pharmaceutically acceptable leaving group which when administered in vivo, is capable of providing a compound wherein R2 is H or phosphate; sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl, benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given above, a lipid, including a phospholipid, an amino acid, peptide, or cholesterol; and
R3 is acyl, alkyl, phosphate, or other pharmaceutically acceptable leaving group which when administered in vivo, is capable of being cleaved to the parent compound.
In a second embodiment, a 2xe2x80x2-fluoronucleoside is provided of the formula: 
wherein the substituents are as defined above.
In a third embodiment, a 2xe2x80x2-fluoronucleoside is provided of the formula: 
wherein the substituents are as defined above.
In a fourth embodiment, a 2xe2x80x2-fluoronucleoside is provided of the structure: 
wherein the substituents are as defined above.
These 2xe2x80x2-fluoronucleosides can be either in the xcex2-L or xcex2-D configuration. The xcex2-L configuration is preferred.
The 2xe2x80x2-fluoronucleosides are biologically active molecules which are useful in the treatment of hepatitis B, hepatitis C or HIV. The compounds are also useful for the treatment of abnormal cellular proliferation, including tumors and cancer. One can easily determine the spectrum of activity by evaluating the compound in the assays described herein or with another confirmatory assay.
In another embodiment, for the treatment of hepatitis or HIV, the active compound or its derivative or salt can be administered in combination or alternation with another antiviral agent, such as an anti-HIV agent or anti-hepatitis agent, including those of the formula above. In general, in combination therapy, an effective dosage of two or more agents are administered together, whereas during alternation therapy, an effective dosage of each agent is administered serially. The dosages will depend on absorption, inactivation, and excretion rates of the drug as well as other factors known to those of skill in the art. It is to be noted that dosage values will also vary with the severity of the condition to be alleviated. It is to be further understood that for any particular subject, specific dosage regimens and schedules should be adjusted over time according to the individual need and the professional judgment of the person administering or supervising the administration of the compositions.
Nonlimiting examples of antiviral agents that can be used in combination with the compounds disclosed herein include 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane (FTC); the (xe2x88x92)-enantiomer of 2-hydroxymethyl-5(cytosin-1-yl)-1,3-oxathiolane (3TC); carbovir, acyclovir, interferon, famciclovir, penciclovir, AZT, DDI, DDC, D4T, abacavir, L-(xe2x88x92)-FMAU, L-DDA phosphate prodrugs, and xcex2-D-dioxolane nucleosides such as xcex2-D-dioxolanyl-guanine (DG), xcex2-D-dioxolanyl-2,6-diaminopurine (DAPD), and xcex2-D-dioxolanyl-6-chloropurine (ACP), non-nucleoside RT inhibitors such as nevirapine, MKC-442, DMP-266 (sustiva) and also protease inhibitors such as indinavir, saquinavir, AZT, DMP-450 and others.
The compounds can also be used to treat equine infectious anemia virus (EIAV), feline immunodeficiency virus, and simian immunodeficiency virus. (Wang, S., Montelaro, R., Schinazi, R. F., Jagerski, B., and Mellors, J. W.: xe2x80x9cActivity of nucleoside and non-nucleoside reverse transcriptase inhibitors (NNRTI) against equine infectious anemia virus (EIAV).xe2x80x9d First National Conference on Human Retro viruses and Related Infections, Washington, D.C., Dec. 12-16, 1993; Sellon D.C., xe2x80x9cEquine Infectious Anemia,xe2x80x9d Vet. Clin. North Am. Equine Pract. United States, 9: 321-336, 1993; Philpott, M. S., Ebner, J. P., Hoover, E. A., xe2x80x9cEvaluation of 9-(2-phosphonylmethoxyethyl) adenine therapy for feline immunodeficiency virus using a quantitative polymerase chain reaction,xe2x80x9d Vet. Immunol. Immunopathol. 35:155166, 1992.)
A new and completely diastereoselective method for the introduction of fluorine into a non-carbohydrate sugar ring precursor is also provided. The method includes reacting a chiral, non-carbohydrate sugar ring precursor (4S)-5-(protected oxy)-pentan-4-olide, which can be prepared from L-glutamic acid, with an electrophilic source of fluorine, including but not limited to N-fluoro-(bis)benzenesulfonimide, to yield key intermediate fluorolactone 6. The fluorolactone is reduced to the lactol and acetylated to give the anomeric acetate and then used for the synthesis of a number of novel xcex2-L-xcex1-2xe2x80x2-fluoronucleosides. The corresponding D-enantiomer can also be synthesized using D-glutamic acid as a starting material.
In an alternative embodiment, a fluorinated glycal is prepared which is dehydrogenated and then converted to a 2xe2x80x2,3xe2x80x2-dideoxy-2xe2x80x2,3xe2x80x2-didehydro-2xe2x80x2-fluoronucleoside or a xcex2-L or xcex2-D-arabinosyl-2xe2x80x2-fluoronucleoside, as discussed further below.
A method for the facile preparation of 2xe2x80x2,3xe2x80x2-dideoxy-2xe2x80x2,3xe2x80x2-didehydro-2xe2x80x2-fluoronucleosides is also presented that includes the direct condensation of silylated 6-chloropurine with key immediate, which is prepared from L-2,3-0-isopropylidene glyceraldenhyde.